This study of Asian immigrant female venue-based sex workers in New York City (NYC) and Los Angeles (LA) aims to develop strategies for efficiently and effectively targeting HIV risk-reduction interventions to high-risk sex-work venue clusters. Female sex workers are at high risk for sexually transmitted infections, such as HIV, and highly vulnerable to violence and exploitation. A substantial portion of female sex workers are Asian immigrants, whose vulnerability is exacerbated because sex work for immigrant women may be part of a larger strategy to pay off migration debts and to ensure subsistence when there is a lack of other employment alternatives. Most health-related research on sex work has focused on street prostitution, leaving substantial gaps in knowledge about HIV risk for indoor or off-street sex workers, who have become dominant in the sex work industry in recent years. Indoor or off-street sex work occurs in venues such as massage parlors, or is negotiated in venues such as bars and hotels. The growth in the indoor or off-street venue-based sex work industry in NYC has been traced in part to arrests of street-based sex workers, driving sex work into indoor venues. Similarly, in LA, police monitoring of indoor venues such as massage parlors has contributed to expansion of indoor sex work in venues not requiring monitoring and licensure, such as aromatherapy firms and tanning salons. Regarding HIV risk, the few existing studies on immigrant indoor venue-based female sex workers indicate that a combination of factors limit consistent condom use, including coercion from clients, financial incentives and condom use policies at venues. Other research on sex workers in general suggests that HIV risk varies widely by the form of sex work, sex worker and client demographics, and presence of other risk factors, particularly substance use. These factors may cluster geographically, offering an opportunity to more efficiently and effectively target risk reduction interventions. In the proposed study, we aim to 1) test a conceptual model that explains why there are lower rates of HIV sexual risk behavior in some indoor sex work venue clusters in order to ascertain the relative importance of sex workers' HIV knowledge and attitudes, venue culture, geographic location and local policy enforcement; and 2) use findings from the first aim to develop venue-level and geographically targeted intervention strategies for efficiently and effectively reducing HIV risk in high-risk sex-work venue clusters. The study uses GIS mapping of sex-work venue locations, in- depth interviews with sex workers, and an analysis of local policies regulating indoor venue-based sex work. Two sites (NYC and LA County), comprising the largest concentrations of Asian immigrant populations in the US, and three ethnic immigrant sex worker populations (Chinese, Korean, and Vietnamese) are the focus for data collection and analysis. Findings will form the foundation for future studies to develop and test geographically targeted risk reduction interventions aimed at high-risk indoor sex work venues and venue clusters.